Prognostic Importance of Ki-67 in Breast Cancer and Its Relationship with Other Prognostic Factors.

Objective The clinical feature of breast cancer is very heterogeneous because of the variable prognostic factors impact its behaviour. The aim of study is to find the prognostic importance of Ki-67 and to analyse the correlation between Ki-67 index and the other conventional prognostic factors in breast cancer patients. Materials and Methods Between 2010 and 2017, patients with invasive ductal carcinoma who received radiotherapy after surgery were included in study. A single pathologist re-defined of all cases retrospectively. Ki-67 were established three categories based on Ki-67 levels: low (<10%), intermediate (10-25%) and high (>25%). Results A total of 258 patients were included. 46 of 258 (18%) patients were in low, 82 of 258 (32%) patients were in intermediate and 130 of 258 (50%) patients were in high Ki-67 group. There were no correlations between menopausal status, age, and Ki-67 level. Low-pT stages tended to have low Ki-67 expression (p=0.07). Low-pN stages correlated with low Ki-67 values (p=0.007). Patients with ECE (+) were prone to have higher Ki-67 values (p=0.02). The significant correlation was seen between Ki-67 and tumour grading (p=<0.0001). Patients with LVI (+) had higher Ki-67 expression (p=0.007). Luminal A tumours were correlated with low Ki-67 group (p=<0.0001). Ki-67 values had significant effect on DFS (p=0.03) but not OS (p=0.09). Conclusion This study showed that high Ki-67 expression is associated with higher pT-stage, higher pN-stage, higher grade, ER/PR negativity, HER2/neu positivity, ECE and LVI positivity. The prognostic impact of Ki-67 was only demonstrated for DFS.